Fitting indicator bulb in L549 rear light.

[Mr Spigot]

My 1960 saloon has the original Lucas L549 rear light units which house the rear and brake lights. A separate indicator light (Lucas L488) has been fitted by drilling a hole in the wing just above it, a common upgrade and it all works well. I am about to have two new wings fitted (the old ones have rust) and rather than drill holes in them for the indicators, I was looking at fitting a bulb holder within the light unit to take an amber LED bulb.
I have seen others make these up and they work very well, and you can buy a kit from Better Car Lighting to do this, https://www.bettercarlighting.co.uk/ind ... ductId=637 , but at nearly £240 plus postage, it is not a cheap option!
Has anyone done this themselves and if so, how did you do it?
The kit mentioned above turns the bulb holder around so that the twin brake/rear light is at the top, shining through the reflector, and the yellow LED is at the bottom, where the original bulb was.